LED room lights will double as "Li-Fi" wireless nodes

You may be able to say goodbye to the wireless routers that beam Wi-Fi to your home electronics if new research into LEDs starts bearing fruit. A consortium of UK universities led by the University of Strathclyde will be working on technology that sends data signals over the light emitted by illumination-grade LEDs. Their idea is to modulate the LED light with internet communication data and, in so doing, eliminate the need for RF and microwave gear that accomplishes this task today.

The technique of modulating information onto light signals is well known. It is widely used with laser light for some kinds of telecom applications. But it is generally not practical for use with incandescent bulbs or fluorescent lights because the bulbs cannot react quickly enough to a superimposed data signal. But that's not a problem with LED light. The UK researchers say they anticipate reaching data transmission speeds of 1 Gbit/sec with their "Li-Fi" techniques.

To do so, they intend to use GaNi LEDs in an array. The scheme they have in mind would put thousands of "micro LEDs" in a one-square-millimeter area. Each of the LEDs would be potentially modulated with its own data signal. The entire array would be bright enough to serve as an illumination-grade light source for ordinary room lighting.

To some degree, LEDs are already modulated in normal use. Many LEDs used for lighting are driven with pulse-width-modulated signals as a means of dimming the LED light. This technique allows driving the LED with a constant voltage for ever more brief time periods as a way of reducing its light output. This technique is employed as a way of keeping the LED emitting dimmer light at the same color temperature, because LED light color is sensitive to drive voltage. But the modulation frequencies the UK researchers have in mind are far higher than those used for dimming purposes.

The UK consortium is being funded by the Engineering and Physical Sciences Research Council (EPSRC) in the UK and is expected to span the next four years. Much of the work will focus on developing the tiny, micron-sized LEDs which are at the heart of the Li-Fi idea. The tiny LEDs are able to flicker on and off 1,000 times quicker than larger LEDs normally used for illumination-grade work. The LEDs are so tiny that 1,000 of them would fit into the space occupied by a single larger 1-mm2 LED.

Moreover, each micron-sized LED would act as a tiny pixel. That ushers in the idea of using the LEDs in a screen displaying information at exactly the same time as providing internet communications and the overall room lighting. Professor Martin Dawson of the University of Strathclyde, who is leading the initiative, says: “Imagine an LED array beside a motorway helping to light the road, displaying the latest traffic updates and transmitting internet information wirelessly to passengers’ laptops, netbooks and smartphones. This is the kind of extraordinary, energy-saving parallelism that we believe our pioneering technology could deliver.”

The time frame proposed for all this is about ten years. Researchers say there are still a lot of problems to solve before the technology is ready for prime time. Professor Dawson says: “The Universities of Cambridge, Edinburgh, Oxford and St Andrews are all working with us, bringing specific expertise in complementary areas that will equip the consortium to tackle the many formidable challenges involved – in electronics, computing and materials, for instance – in making this vision a reality. This is technology that could start to touch every aspect of human life within a decade.”